"She is saying "Good evening" to you."
Translation:O sana "İyi akşamlar" diyor.
I think you will understand this better when you learn "noun cases" (Turkish grammatical structure "ismin halleri") but for now you can try to remember it like this: In English some verbs always take a special proposition. For instance you "argue WITH someone". So consider this in this syntax: in Turkish you always use verb "demek" with "-e/-a" noun affix when you mean to say it TO SOMEBODY. So its always: bana dedim. sana dedim. ona dedim. bize dedim. size dedim. onlara dedim.
If you use "-i" affix, it does not mean "say something TO somebody", it means, "say somebody". For instance sana dedim = I said to you. seni dedim = I said(told) about you (to somebody else)
It doesn't have the Dative case so that would mean:
she is saying "Good evening" you